Nobody said its impossible just that the cost would be high. Any good electronics guy that specializes in radio transmission should be able to build you something, back in the day some of us built our own remote calls using parts from regular callers along with various sending units from video recording equipment and they worked well but when the cost of remote callers came down they were obsolete.
I believe there are some remotes out there that will run multiple callers that would accomplish what you want.
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After the first shot the rest are just noise.
Make mine a Minaska.
Heaven has rules and walls, He-l has open borders